Existing rechargeable devices, such as vacuum cleaners, may use a direct current (DC) motor that is powered by a rechargeable battery, where the battery is charged by an auxiliary circuit connected to an alternating current (AC) power supply, such as a standard wall outlet. When the device is plugged into the AC power supply, the AC supply is effectively converted to DC and used to charge the battery while providing power to the DC motor. When the AC power supply is removed, the battery may continue to provide DC power to the motor. When AC power is used, the AC is converted into DC and stepped down to match the battery power level. DC motors using battery supplied power may be relatively weak compared to AC power motors using the same outlet source.
In other consumer devices, a universal motor may be used to power the device. Universal motors accept both AC and DC power without the need for an AC-DC conversion circuit. These universal motors are usually series wound circuits in which the motor field coils are connected in series. The problem with universal motors is that often, the voltage from an AC source is higher than the voltage from a DC battery, and thus a huge power discrepancy exists in switching between an AC outlet source and DC battery power supply. This difference in power is very noticeable and further highlights the poor performance of a universal motor using battery-only power.
Therefore, there is a need to provide a circuit for a rechargeable motor that will enable the motor to run on both an AC outlet source and DC battery, preferably with less discrepancy in power when switching between AC and DC power.